The present invention relates to a liquid ejecting apparatus.
A printer that prints by ejecting ink droplets from a recording head toward a recording medium is known as a liquid ejecting apparatus for ejecting a liquid onto a target. In conventional printers, solvents of ink may vaporize within a recording head and the vaporized solvents may diffuse from nozzles of the recording head. If this happens, viscosity of the ink in the recording head increases. The increased ink viscosity may clog the nozzles, or may cause dust to adhere to the nozzles. Also, air bubbles may enter from the nozzles into the recording head when the ink cartridge is replaced. Such entry of air bubbles and clogging of the nozzles may cause printing failures.
To prevent printing failures, conventional printers perform a cleaning operation for aspirating ink out of nozzles of the recording head. By aspirating ink out of the nozzles, such nozzle problems as clogging, adhesion of dust, and entry of air bubbles are prevented.
The following describes the cleaning operation in detail. A cleaning mechanism arranged in a printer typically performs the cleaning operation. The cleaning mechanism includes a cap for covering nozzles of a recording head, an ink drain path that is connected to the cap, and a depressurizing pump arranged midway on the ink drain path. The cap is placed to cover the nozzles of the recording head, and the depressurizing pump is driven, so that the inner pressure of the cap is decreased. This causes ink to be aspirated out of the nozzles of the recording head. The aspirated ink is drained via the ink drain path. With this operation, clogging of the nozzles is prevented.
A conventional printer for color printing uses inks of plural colors, e.g., Cyan, Magenta, Yellow, and Black. The printer using inks of plural colors has, on its recording head, nozzle rows whose number corresponds to the number of the colors. Such a printer may perform the cleaning operation by covering all the nozzle rows on the recording head with a cap, and aspirating ink out of all the nozzle rows at the same time.
With this cleaning operation, however, ink is aspirated even from nozzles that are not clogged. As a result, excess ink is consumed. To reduce such wasting of ink, Japanese Laid-Open Patent Publication No. 2000-225715 proposes a cleaning mechanism that selectively aspirates ink only from nozzle rows that require cleaning.
In detail, a cap of this cleaning mechanism has a plurality of chambers. A plurality of ink drain paths in one-to-one correspondence with the chambers are arranged between the chambers and a depressurizing pump. Each ink drain path has a valve. During the cleaning operation, a valve on each ink drain path is adjusted to open and close according to the clog state of the corresponding nozzle row. Among the plurality of chambers of the cap, only a chamber connected to an ink drain path whose valve is open is depressurized. Ink is aspirated out of the nozzle row corresponding to the depressurized chamber. In this way, this cleaning mechanism aspirates ink only from nozzle rows that require removal of clogging, so that wasting of ink is reduced.
To improve color reproduction and gloss of a printed image, a printer that ejects reactive ink from its recording head in addition to normal color ink is conventionally known. The reactive ink includes clear (colorless) ink. The reactive ink coagulates with color ink on a recording medium, to improve color reproduction and gloss of a printed image.
When the printer that uses reactive ink performs the cleaning operation, color ink and reactive ink may react and coagulate within a cap. This may degrade the function of the cleaning mechanism. To prevent such a coagulating reaction of color ink and reactive ink within the cap and prevent degradation of the cleaning mechanism function, this printer may also employ the above-described cap, which has a plurality of chambers.
The above-described cap has its case unit being divided into a plurality of chambers by a partition wall. During the cleaning operation, an upper edge of the case unit and an upper edge of the partition wall simultaneously come into contact with the nozzle surface of the recording head.
When this cap is brought into contact with the nozzle surface, however, the upper edge of the case unit and/or the upper edge of the partition wall may be stress-deformed under a load, which is caused by a spring pressing the cap. For example, the upper edge of the partition wall may come in close contact with the nozzle surface, whereas the upper edge of the case unit may not come in close contact with the nozzle surface. In this way, the cap may often unevenly come into contact with the nozzle surface. Such uneven contact between the cap and the nozzle surface lowers sealing performance of the cap, and degrades the function of the cleaning mechanism.
To solve this problem, one technique is known to form a part of the cap that comes into contact with the nozzle surface using an elastic material, such as an elastomer. This technique ensures close contact and tight sealing between the cap and the nozzle surface by bringing the cap into contact with the nozzle surface with a relatively strong force and excessively deforming the elastomer.
However, a relatively large amount of energy is required to bring the cap into contact with the nozzle surface with a relatively strong force. This may require a larger motor to be used for the cleaning operation, and may increase the cost of the printer. This may also cause wear of a driving unit for operating the cap, and may reduce durability of the printer.